The content of negative oxygen ions is one of the important indications of air quality. The United Nations regulates that the standard of a clean air is 1000-1500 negative oxygen ions/cubic centimetres, and up to 100 thousands of negative oxygen ions/cubic centimetres are in forest districts; however, merely dozens or hundreds of negative oxygen ions/cubic centimetres are generally in cities of China, and as low as a dozen of negative oxygen ions/cubic centimetres may be in many enclosed buildings.
At present, most of the techniques for producing negative oxygen ions produce space free electrons through discharging, and the electrons are then combined with oxygen to form negative oxygen ions; but, at this time, harmful substances such as ozone and oxynitrides are also produced, which becomes an obstacle to the popularization and application of such a dry-type negative oxygen generator.
At present, there is a fullerene negative oxygen ion release agent internationally, which, however, is not extensively used yet due to a higher price.
Therefore, there is a desire for a method and device for producing negative oxygen ions, which can produce a large number of negative oxygen ions with a high efficiency at a low cost, without producing any harmful substances such as ozone.
In addition, with the aggravation of haze phenomenon, the demand for air purifiers is increasing day by day in recent years. At present, air purifiers are mostly of filtration type, i.e. air is sent to a filter by a draught fan, and passes through various filter screens having different functions and respectively achieving the effects of removing crude, medium and fine particulate matters by filtration; furthermore, there are filter screens having physical capture and chemical decomposition functions: a mineral crystal membrane, a photocatalyst decomposition membrane, an HEPA membrane, etc.
The common characteristic of the above air purifying techniques is using filter membranes to capture particulate matters in the air; when the operating time is longer or the environment is harsh, dust particles will block pores very fast, the purifying effect is decreased, and it is necessary to change consumables such as filter screens, which greatly increases the effective usage cost.
There are also some cases where high voltage electrostatic dust collection methods are used to control particulate matters in the air, which have a lower efficiency and may produce harmful substances such as ozone.
In recent years, the use of plasma or net ion flow purifiers rises abroad, which can effectively remove PM 2.5, but is difficult to popularize due to excessively high costs.
Therefore, there is a further desire for a method and device for purifying air, which can purify air with a high efficiency at a low cost, without producing any harmful substances such as ozone, and are long-acting and free of maintenance without changing consumables such as filter screens.